The present invention relates to a process for constructing electronic devices wherein a substrate is coated with a conducting layer that is further coated with a thick film paste. The thick film paste may contain materials such as glass frit, various conductors, photo-imageable polymers and, usually a solvent. In the fabrication of these devices photo-definable protective layers may be used to isolate photoimageable thick film deposits from other elements of these electronic devices such as conductive layers. A problem arises in some of these devices in that the solvent used in the thick film pastes, usually an ester or ether type solvent, is frequently aggressive to the polymer protective layer and may lead to short circuits. This can lead to problems on the surface of the substrate such as pealing or dissolution of the of the protective layer from the substrate when that layer is exposed to the thick film paste.
Wang et al in the Proceedings of the SPIE—The International Society for Optical Engineering (1999) vol. 3906, p. 619-24 describe the electrical characterization of polymer thick film resistors.
Fukuda et al (U.S. Pat. No. 5,601,638) describes a thick film paste for use in the formation of circuit components.
Ezaki (U.S. Pat. No. 5,362,927) reports a thick film hybrid circuit board device formed by lamination.
Kazunori et al (JP 2001155626 A) provide a method for producing a display substrate.
Takehiro and Shigeo (JP10340666 A) describe a field emission element.
Kazunori and Shinsuke ((JP 2001111217 A) provide a method of forming laminated wiring.
The present invention addresses the problem of incompatability of the thick film paste and the protective layers on the substrate by fabricating a protective layer from positive photo-imageable materials which do not degrade or dissolve upon contact with the high boiling ester-type or ether-type solvents found in the photo-imageable thick film pastes.